This invention relates to deodorant compositions.
Zinc oxide is known to have bactericidal properties, and has been widely used in deodorant compositions. It is believed to work by the zinc ions of the zinc oxide going into solution in the outer layer of the skin, where they kill microorganisms by preventing enzymes therein from functioning properly.
Inhalation of zinc oxide particles smaller than about 10 micrometers can cause adverse reactions in humans and animals. For this reason, many countries have adopted Health and Safety legislation forbidding the use of zinc oxide particles smaller than 10 micrometers in aerosols. This places a lower limit on the size of zinc oxide particles that can be used in aerosol deodorant compositions.
Although zinc oxide particles can easily be made to a size greater than 10 micrometers, such particles appear as a white powder and are considered unsightly. In order to avoid this white appearance it would be necessary to use a zinc oxide particle size below 10 micrometers, but this would not be permitted under the legislation referred to above.
Spherical particles comprising a zinc oxide coating are known. Thus, U.S. Pat. No. 5,407,743 describes electromechanical devices such as transducers which comprise glass spheres of size 1 to 500 microns coated with zinc oxide. The zinc oxide coating is formed by applying a zinc oxide precursor to the spheres and then contacting the coated spheres with an oxidizing agent to form a zinc oxide coating on the spheres.
J. Soc. Cosmet. Chem., 41, 197xe2x80x94207 (May/June 1990) describes a mechanochemical process wherein fine particle zinc oxide is mixed with spherical resin cores to provide a hybrid powder of cores with their surfaces uniformly covered with zinc oxide. The powder has deodorizing qualities.
We have now devised some deodorant compositions containing zinc oxide, or a zinc salt, whereby one or more of a number of advantages over prior known compositions can be obtained including, if desired, the advantage of substantially transparent zinc oxide (or zinc salt) without the need to use particles having a size below 10 micrometers.
According to one aspect of the invention, we provide a deodorant composition for topical application, which comprises a plurality of particles which each comprise a glass microsphere at least partially coated with a zinc compound sintered to the glass microsphere, the zinc compound being selected from zinc oxide, a zinc salt or any mixture of two or more thereof, said particles being dispersed in a carrier.